1. Field of the Invention
This invention generally relates to a switching circuit, and more particularly to a switching circuit using semiconductor devices for fade-in and fade-out operations.
2. Description of the Prior Art
Generally, a fade-in or fade-out operation is utilized as a special effect in a radio or a television. The fade-in or fade-out operation can be performed in such a manner that a signal gain is manually and gradually varied or that a circuit is used by which the signal gain is automatically varied for a given time. However, the manual control is inconvenient for consumers. And in the automatic control, the arrangement of the circuit is complicated and a fade-in time interval or a fade-out time interval cannot be varied. Accordingly, the automatic control is inconvenient and not practical.